The invention relates to a polarized relay, and more particularly to a polarized relay having three stable states.
A relay of this kind can be used for example for controlling a commutator motor. This particularly applies when the relay has a tri-stable behavior and the three stable states, and hence, exhibits tri-stable behavior. This tri-stable behavior of the relay can be associated with the motor states "resting," "clockwise running" and "counter-clockwise running."
German Patent No. DE 32 43 266 C2 discloses a polarized relay which consists of two first yokes of U-shaped cross-section facing each other with their short arms and of smaller second yokes enclosed by these at a distance. Between the first and second yokes is a permanent magnet with magnetic axis running at right angles to the large faces of the yokes. The second yokes further comprise an exciter coil which encloses a rod-like armature displaceable in the direction of the coil axis and whose two ends lying outside of the exciter coil are designed as plates which are displaceable between the inner faces of the short arms of the first yokes forming the pole faces, and the end faces of the second yokes. The armature consists of two rod halves divided radially in the center of the exciter coil and between which is mounted a coil compression spring which is tensioned so that the plates of the armature in the currentless state of the exciter coil adjoin the pole faces of the short arms of the first yokes, while in the current-flowing state of the exciter coil, depending on the current flow direction, either the one or the other plate adjoins the corresponding end faces of the second yokes.
This relay shows a tri-stable behavior when using only one exciter coil. Moreover, it has a very expensive and complicated construction of the relay which has in addition to the exciter coil and its twin-divided armature a compression spring, two permanent magnets and four yokes. Furthermore with each switching process the spring force of the compression spring must be overcome by the force of the magnetic field built up by the exciter coil which requires correspondingly high exciter currents.
German Patent No. DE 35 46 382 A1 discloses a polarized electrical mini relay which is formed as a two-fold switch-over relay. A leaf armature and reflux elements are mounted at each of the two free ends of a coil core. The leaf armatures are held by permanent magnets set in series and carry out a synchronous switching process during excitation of the coil.
This two-fold switch-over relay is only provided for a mono- and bi-stable operation. It has the further disadvantage that the design of the reflux elements requires a lot of soft iron in order to ensure the magnetic reflux which is required for a secure function of the relay.
European Patent No. EP 0 474 904 A1 discloses a commutator gear drive unit with an IC block, two motor relays and the brushes of the commutator motor mounted on a conductor plate, but this arrangement is relatively expensive and requires a significant amount of space as a result of using two motor relays.